Traffic control system



Patented Nov. 27, 1934 1,982,341 TRAFFIC coN'rnoL srs'rniu Richard 0. Hitchcock, Wilkinsburg, Pa, assignor to Westinghouse Electric 85 Manufacturing. Company, a corporation of Pennsylvania Application March 24, 1931, Serial No. 524,800

6 Claims (01.117-329) v My invention relates to trafiic-control systems and has particular relation to street devices adapted to regulate the operation of a system of tramc signals.

' The term street, devices is ordinarily applied, in the prior art, to devices that are disposed along the highways at intersections in such positions as to respond to the presence of a vehicle.

By reason of its coaction with the vehicle, a traffic signal, disposed at a highway intersection, is

actuated to display a go signal for the particular highway along which the vehicle is permitted to move. I

A number of devices of this type have been proposed. Of these, the most generally known are:

1. A mechanical device thatis adapted to respond to the pressure exerted by a vehicle by reason of its weight.

2. An'acoustic device that is adapted to respond to the sound emitted by the horn of a vehicle 3Q A photo-sensitive? device comprising a'source of .light that projects a beam to a photo-tube which is adapted to be obstructed by the presence of a vehicle a While the street devices of the prior art have their particular advantages, each of them has a comparatively aggravating disadvantage which so renders it undesirable in certain connections.

Thus, the mechanical device necessitates an excavation in thestreet when it is installed or when it isserviced ,or repaired.

The acoustic device, of the type described hereinabove, has thedisadvantagethat it is dependent, for its operation, on the sound emitted by a vehicle of any general type. It can, therefore, not

be rendered selective and, in many instances, responds to ordinary street sounds. The continual noises produced by the horns of the vehicles passingan intersection, wherein the acoustic device is installed, render the neighborhood unsatisfactory for residential purposes.

The photo sensitive device, while not subject to the above objections, has the disadvantage that it is not applicable in a, region subject to frequent fogs. Furthermore, adjustment of the light source of the photo-sensitivedevice, relative to the photo-tube, is a comparatively delicate matter and may occasion some difiiculty.

d It is, accordingly, an object of my invention to provide a street device capable of universal application.

55 A more specific object of my invention is to provide a selective street device of the acoustic type.

Another specific object of my invention is to provide a street device of the acoustic type that shall operate without disturbing the neighbor'- $0 hood wherein it is installed.

A further specific object of my invention is to provide a street device of a type that shall not require an excavation in the highway whereon it is disposed.

An ancillary object of my invention is to'provide a street device of a type that shall respond to vehicles moving along only one side of the center line of a highway whereon it is disposed.

More concisely stated, it is an object of my in- 'vention to provide a tractable street device of comparatively rugged character that shall be capable of installation without considerable expense and that shall require little servicing.

According to my invention, Iprovide an acoustic street device of a type entirely distinct from the acoustic device constructed as taught by the prior art. It will be noted .that the acoustic street device of the prior art depends, for its operation, on the coaction of a horn disposed on 30 the vehicle and on'a receiver disposed in the street.

e As has been pointed out hereinabo've, it is thereby rendered unselective.

Essentially, my improved device comprises a sound transmitter adapted to transmit-sound of a predetermined frequency which is preferably in the supersonic range of the sound spectrum, and.

a receiver adapted to respond to the sound. The receiver is, in turn, associated with the relays for regulating the operation of the street signals and, i

when its condition is changed, byreason of the presence of a vehicle along a trafiic lane, the

street signals respond.

I have found that the sound transmitted by the sound-generating system should be preferably of a frequency of 25000 cycles. Sound of this frequency may be generated bya magneto striction oscillator and is capable of being. directed in a of sufiicient accuracy to be usable in the present application. As a matter of fact, their very crudeness lends to the apparatus described herein the advantage of not requiring accurate alinement of the transmitter and the receiver. 1

In the present application, several modifications of my invention are illustrated. In particular, the modifications of my invention consist in variations in the orientation of the transmitter relative to the receiver. 5

In one modification of myinveritionfthe reciver is disposed on one side and the transmitter on the opposite side of a.highway, the one being oriented relative to the other in such manner that. the beam of sound is horizontal.

' In another modification of my invention, the transmitter and the receiver are disposed on the same side of the highway and are so oriented relative to each other that a vehicle, moving on one side of the center line of the highway, reflects the beam from the transmitter into the. receiver, while a vehicle, moving along the other side of the center line, is not effective to reflect the beam into thereceiver. It will be noted that the particular arrangment of the apparatus has the adyantage that a vehicle moving up to an intersection may actuate the traffic signals, whilea ve- -hicle moving away from an intersection does not operate them,

The same object is also accomplished by another modification of my invention, wherein the receiver and the transmitter are disposed on opposite sides of the highway but are so oriented that an angular beam of sound is projected from the transmitter to the receiver. The beam is of V such inclination that it is interrupted by vehicles moving along one side of the highway but is not interrupted by vehicles moving along the remaining, side of the highway. I

The novel'features that I consider characteristic of my invention are set forth with particularity in the appended claims.- The invention itself, however, both as to-its organization and its method of operation, together with additional objects andaavantages thereof, will best beunderstood from the following description of specific embodiments, when read in connection with the accompanying drawing, in which:

Figure 1 is a diagrammatic view showing the" principal elements of the transmitter.

Fig. 2' is a schematic view showing the disposition of ,a receiver and a transmitter in an embod-- iment of my invention.

Fig. 3 is a schematic view showing the disposltion of a transmitter and the receiver in a modification .of my invention, and,

Fig. 4 is a schematic view illustrating afurther modification of my invention.

The apparatus shown in Fig. 1 comprises an oscillator (or sound generator) including a; thermionic tube 3 between the grid 5 and the plate '7 of which a variable capacitor 9 and an inductor 11 are connected. The windings 13' of the inv ductor 11 are traversed by a rod 15 particularly The oscillatory circuit 1 is tuned to the desired frequency, and, in consequence thereof, the magneto-striction rod 15 has a longitudinal vibration of this frequency. The sound waves generated by the vibrating bars are collineated by a parabolic reflector 21 and directed along a predetermined line.

and a unit 25, comprising a microphone 27, an amplifier 29 and a relay 31, of a requisite type, are shown, schematically, disposed on the remaining'side of a highway 23. When the beam of sound emanating from the transmitter 1 is interrupted by a vehicle 33, the relay-31 is actuated to cause a system of trafiic signals 34 to operate in a required manner.

It is to be noted that the amplifier 29 is tuned to the frequency of the oscillations received by the microphone 27 from the transmitter 1, and,

consequently, is rendered selectively responsive only to the sound of the transmitter. It does not, therefore, respond to ordinary street sounds.

In Fig. 3, the receiver 25 is shown as disposed on the same side of the highway 23 as the transmitter '1. These elements are so oriented relative to each other that a vehicle 33, moving on oneside of the center line of the highway 23, refleets a beam of sound from the transmitter 1 to the receiver 25 to cause the traflic signals to be actuated. On the other hand, a vehicle moving in the opposite direction and, therefore, moving along the remaining side of the highway does not actuate the system. i

In Fig. 4, the transmitter. side of the highway 23 sends an inclined beam of sound to the receiver 25 disposed on the remaining side of'the highway. Here, the receiver 25 is energized only when the beam of sound is interrupted by a vehicle 23 moving along one side of the center line of the highway.

It is to be noted that an oscillator of a specifi type has been shown as incorporated in the trans- However,the magneto-striction oscillator appears to have considerable advantage in the present connection, in view ,of the fact that it is comparatively simple to construct and is'capable of maintaining a comparatively uniform frequency for a considerable period of time.

Although I have shown and described certain specific embodiments of my invention, I am fully aware that many modifications thereof are possible. My invention, therefore, is not to be restricted except insofar as is necessitated by the prior art and by the spirit of the appended claims. I claim as my invention: 1. In a trafiic control system for a highway having two-way tramc on its surface in combination means for generating a beam of super sonic air waves, means disposed on one side of said highway for supporting said generating means in such mannerv that said waves are projected in a direction to intersect the path of trafilc moving only along one side of 'a predetermined line longitudinal of said highway, means to respond to said waves disposed on the other side of said highway and trafllc control means to respond. to the condition of said wave-responsive means as it'is varied under the influence of traffic moving along said highway.

- 2. In a traflic control system for a highway in combination means for generating a beam' of supersonic air waves, means for supporting said 1 disposed on one generating means in such manner that said waves are projected across said highway in a direction to intersect the path of traffic moving only along one side of a predetermined line longitudinal of said highway, means to respond to said waves and trafiic signalling means to respond to the condition of said wave-responsive means as it is varied under the influence of traflic moving along said highway.

3. In a trafllc control system for a highway in combination means for generating a beam of air waves, means disposed on one side of said highway for supporting said generating means in such manner that said waves are projected across said highway in a direction to intersect the path of traffic moving only along one side of a predetermined line longitudinal of said highway, means to respond to said waves, disposed on the same side of said highway as said supporting means forsaid generating means and trafiic con trol means to respond to the condition of said wave-responsive means as it is varied under the influence of traflic moving along said highway.

4. In a system for regulating trafllc along a highway, a device comprising means for the substantially linear projection of a wave-disturbance in the medium surrounding the highway, means responsive means thereat to receive said disturb-v ance and means to respond to an interference of the linear projection of said wave-disturbance onsaid responsive means. 7

5. In a system for regulating traffic along a highway, a' device comprising means for the subof the linear'projection of said wave-disturbance:

on said responsive means.

6. In a systemifor regulating traflic along a highway, a device comprising means for the substantially linear projection of a wave-disturbance in the medium surrounding the highway, means for so supporting said generating means that said disturbance is projected across the highway along aline at such an angle to the horizontal as to be capable of being intersected by traflic moving along one side of a predetermined line longitudinal of said highway but substantially incapable of being intersected by traflic moving along the highway on the other side of said line, means to respond to said disturbance, means for supporting said responsive means to receive said disturbance and means to respond to an interference of the linear projection of said wave-disturbance on said responsive means. I

RICHARD c. mTcHcocK. 

